Ammonium bifluoride (NH5F2) is a chemical compound. It dissolves in water and forms hydrofluoric acid. It can etch glass and corrode metals.
| IUPAC name | Ammonium hydrogen fluoride |
| Molecular formula | [NH4] [HF2] |
| CAS number | 1341-49-7 |
| Synonyms | Ammonium acid fluoride, Ammonium hydrofluoride, Ammonium difluoride, Ammonium hydrogendifluoride, Ammonium hydrogen difluoride |
| InChI | InChI=1S/F2H.H3N/c1-3-2;/h;1H3/q-1;/p+1 |
Ammonium Bifluoride Properties
Ammonium Bifluoride Formula
The formula of ammonium bifluoride is [NH4] [HF2] or [NH4]F·HF. It indicates that the compound contains an ammonium cation ([NH4]+) and a bifluoride or hydrogen (difluoride) anion ([HF2]−). The formula can also be written as NH5F2, which shows the number of atoms of each element in the compound.
Ammonium Bifluoride Molar Mass
The molar mass of ammonium difluoride is 57.044 g/mol. It is calculated by adding the atomic masses of the elements in the formula: (14.007 + 4 × 1.008) + (2 × 18.998) = 57.044 g/mol.
Ammonium Bifluoride Boiling Point
The boiling point of ammonium difluoride is 240 °C (464 °F; 513 K). However, the compound decomposes before reaching this temperature, releasing ammonia and hydrogen fluoride gases1. Therefore, ammonium difluoride does not have a true boiling point.
Ammonium Bifluoride Melting Point
The melting point of ammonium difluoride is 126 °C (259 °F; 399 K). It is the temperature at which the solid compound changes into a liquid. The melting point depends on the strength of the intermolecular forces between the molecules of the compound.
Ammonium Bifluoride Density g/ml
The density of ammonium difluoride is 1.50 g/ml. It is the mass of the compound per unit volume. The density can be measured by dividing the mass of a sample by its volume. The density of a substance depends on its molecular structure and packing.
Ammonium Bifluoride Molecular Weight
The molecular weight of ammonium difluoride is 57.044 g/mol. It is the same as the molar mass of the compound. The molecular weight can be used to calculate the number of moles of a substance in a given mass or volume.
Ammonium Bifluoride Structure
The structure of ammonium difluoride is cubic, related to the CsCl structure. It means that the compound has a crystalline lattice with a cubic unit cell, where each ammonium cation is surrounded by four fluoride centers in a tetrahedron, and each difluoride anion is linear. The structure can be represented by a three-dimensional model or a two-dimensional diagram.
Ammonium Bifluoride Solubility
The solubility of ammonium difluoride in water is 63 g/100 ml at 20 °C. It means that 63 grams of the compound can dissolve in 100 milliliters of water at this temperature. The solubility depends on the polarity and hydrogen bonding ability of the compound and the solvent.
| Appearance | Colourless crystals or white crystal |
| Specific gravity | 1.50 |
| Color | Colorless |
| Odor | Slightly sharp, pungent |
| Molar mass | 57.044 g/mol |
| Density | 1.50 g/cm3 |
| Melting point | 126 °C (259 °F; 399 K) |
| Boiling point | 240 °C (464 °F; 513 K) (decomposes) |
| Flash point | Non-flammable |
| Water solubility | 63 g/100 ml (20 °C) |
| Solubility | Slightly soluble in alcohol, insoluble in liquid ammonia |
| Vapour pressure | Not available |
| Vapour density | Not available |
| pKa | Not available |
| pH | Not available |
Ammonium Bifluoride Safety and Hazards
Ammonium difluoride is a toxic and corrosive chemical that can harm you if you swallow it, breathe it, or touch it. It can cause severe burns and eye damage, nosebleeds, cough, wheezing, shortness of breath, nausea, vomiting, and loss of appetite. It can also release hydrogen fluoride gas when heated, which is very dangerous to inhale. You should avoid contact with this chemical and wear protective gloves, clothing, eye and face protection when handling it. If you get exposed to it, you should rinse with water and seek medical attention immediately. You should also wash any contaminated clothing before reuse.
| Hazard symbols | T, C |
| Safety description | S26, S36/37/39, S45 |
| UN IDs | UN 1727 (solid), UN 2817 (solution) |
| HS code | 2826.19 |
| Hazard class | 8 |
| Packing group | II |
| Toxicity | LD50 oral (rat) = 200 mg/kg |
Ammonium Bifluoride Synthesis Methods
Different methods can prepare ammonium difluoride, an inorganic salt. Some of the common methods are:
- Vapor phase process: This method involves the reaction of ammonia gas and hydrogen fluoride gas at high temperatures and pressure. The product is a dry and pure ammonium difluoride powder. However, this method requires complex equipment and high investment.
- Liquid phase method: This method involves the reaction of aqueous solutions of ammonia and hydrogen fluoride or ammonium fluoride and hydrofluoric acid at moderate temperature and pressure. The product is a wet and less pure ammonium difluoride crystal. People use this method widely because it is simple, but the product has low quality and tends to absorb moisture and cake.
- Neutralization method: This method involves the reaction of unsaturated ammonium fluoride solution and hydrofluoric acid, followed by the addition of ammonia solution to neutralize the excess hydrofluoric acid. The product is a relatively pure and stable ammonium difluoride crystal. This method can improve product quality and reduce environmental pollution.
Ammonium Bifluoride Uses
Ammonium difluoride is an inorganic salt that has various uses in different industries. Some of the common uses are:
- Glass etching: Ammonium difluoride can attack the silica component of glass and create patterns or designs on the surface. It can also remove stains and rust from glassware.
- Metal treatment: Ammonium difluoride can act as a complexing agent with some metals and improve the quality and appearance of electroplating. It can also remove oxides and scales from metal surfaces.
- Ceramic production: Used as a flux in the preparation of ceramic glazes and enamels. It can also lower the melting point and viscosity of some ceramic materials.
- Organic synthesis: Used as a catalyst or a reagent in some organic reactions, such as fluorination, deprotection, and cleavage.
- Mineral digestion: Also used as a powerful fluorinating agent to convert some refractory minerals and oxides into soluble fluorides. This can facilitate the recovery of valuable metals from ores.
Questions:
Q: What is the bulk density of ammonium bifluoride salts?
A: The bulk density of ammonium difluoride salts is 1.5 g/cm3.
Q: What is ammonium bifluoride used for?
A: Ammonium difluoride is used for various purposes, such as glass etching, metal treatment, ceramic production, organic synthesis, and mineral digestion.
Q: How to etch glass with ammonium bifluoride?
A: To etch glass with ammonium difluoride, you need to prepare a solution of the salt in water and apply it to the glass surface with a brush or a stencil. The solution will react with the silica component of the glass and create patterns or designs. You need to rinse the glass with water and dry it after etching.
Q: Is ammonium bifluoride safe on chrome wheels?
A: Ammonium difluoride is not safe on chrome wheels, as it can corrode the metal and damage the finish. It can also cause severe burns and eye damage if it comes in contact with skin or eyes. You should avoid using ammonium difluoride on chrome wheels and use a suitable cleaner instead.
Q: What is the shelf life of ammonium bifluoride?
A: The shelf life of ammonium difluoride depends on the storage conditions and the purity of the product. Generally, it can last for several years if stored in a cool, dry, and well-ventilated place in a tightly closed container. However, it can absorb moisture from the air and form clumps or cakes over time. You should check the appearance and quality of the product before using it.
Q: Is ammonium bifluoride an acid?
A: Ammonium difluoride is not an acid, but a salt that contains an ammonium cation ( [NH4]+ ) and a difluoride or hydrogen (difluoride) anion ( [HF2]− ). However, it can act as an acid-base compound, as it can release hydrogen fluoride (HF), a strong acid, when heated or dissolved in water.